( -4x^2 -5x+3) - ( 7x^2 +x+6) + ( -6x^2 +6x+2)
Distribute the minus sign into the second term
( -4x^2 -5x+3) + (- 7x^2 -x-6) + ( -6x^2 +6x+2)
Combine like terms
-4x^2 -7x^2 -6x^2 -5x -x +6x +3 -6 +2
-17 x^2 +0x -1
Rewriting
-17x^2 -1
To get the -17x^2, I first distributed the minus sign to the second term so that all the terms had a negative
( -4x^2 -5x+3) + (- 7x^2 -x-6) + ( -6x^2 +6x+2)
Now looking at all the x^2 terms
-4x^2 - 7x^2 -6x^2 = -4-7-6 = -17
The coefficient is -17